OPEC's proven crude oil reserves rose 12.1 percent in 2010 to 1.19 trillion barrels led by Venezuela, which has surpassed Saudi Arabia as the group's largest reserves holder, OPEC said in its Annual Statistical Bulletin.

The latest figures are unlikely to quell skepticism about reserves estimates from the Organization of the Petroleum Exporting Countries, some of which analysts say may be exaggerated although the producers deny doing so.

Iran and Iraq also boosted their reserves last year. In October, Iran increased its reserves to 150 billion barrels within a week of an upward revision by Iraq, ensuring that Tehran continued to rank above Baghdad.

"OPEC has a fantastic history of competitive reserves upgrades," said Bill Farren-Price, analyst at Petroleum Policy Intelligence.

Reserves are one of the criteria OPEC has used in setting output targets. Iran and Iraq were rivals in the past over OPEC quotas and OPEC in the next few years is expected to tackle the issue of bringing Iraq back into the quota system. Iraq is exempt at present.

Iraq boosted its reserves to 143 billion barrels last year, up 24 percent, the report said. Iraq has said its reserves increased as work by international oil companies started to yield results.

Venezuela's move to the No. 1 reserves spot bumps Iran and Iraq to third and fourth place respectively. Commenting on the OPEC report, an Iranian official said the country still held its status as OPEC's second-largest producer after Saudi Arabia.

"Iran is still the second crude producer of OPEC and insists on this," an unnamed Oil Ministryofficial told Iran's state news agencyIRNA on Tuesday.